Penstock Replacement at BUR0026

SGC was appointed by Advance Plus, on behalf of United Utilities, to remove an existing penstock and install a new one within a 4.6 m diameter, 6 m deep shaft near Padiham, Lancashire.

The shaft collects sewage and storm water from a catchment extending around 10 miles across Padiham and the surrounding area. Because of its position in the network it could not be taken out of service, so all the works had to be carried out in a live sewer, in an environmentally sensitive location.

Our scope included:

• Design and installation of a temporary overpumping system to maintain flows
• Removal of the existing cover slab and construction of a temporary, liftable cover slab
• Temporary stank plates to create a dry working area
• Removal of the old penstock and installation of the new penstock, brackets and spindle

Overpumping kept the network running throughout, with no interruption to service. Otters were present on site, so no work could take place in the two hours before dawn or after dusk, and the programme was planned around these windows. Every excavation, including the shaft, had to be covered whenever the site was unattended, so we designed and built a cover slab that could be lifted on and off each shift, with daily activities tightly sequenced to protect productive time.

To remove operatives from live flows, we produced a safe system of work using stank plates to create a dry point within the shaft. It was accepted by both the principal contractor and the client.

Despite severely limited working windows, the penstock replacement was completed on time and within budget.